Method for inhibiting dezincification of brass

ABSTRACT

A brass alloy with dezincification inhibition capability and good cutting and mechanical properties is provided. The brass alloy includes niobium and brass. Niobium is in an amount ranging from 0.01 to 0.15 part by weight and brass is in an amount ranging from 99.85 to 99.99 parts by weight based on 100 parts by weight of the brass alloy.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims priorityunder 35 USC 120 to co-pending U.S. patent application Ser. No.14/597,164, filed on Jan. 14, 2015, which claims priority under 35 USC119 to of Taiwanese Application No. 103101603, filed on January 16,2014.

FIELD OF THE INVENTION

The invention relates to a brass alloy with dezincification inhibitioncapability and good cutting and mechanical properties, more particularlyto a brass alloy comprising niobium and brass.

BACKGROUND OF THE INVENTION

Brass alloy is mainly composed of copper and zinc. Brass alloy alsocontains a small amount of another metal based on the desired use, suchas lead, tin, aluminum and the like. Compared to copper or other copperalloys, brass alloy has a good cutting property, but exhibits poorresistance to corrosion.

Conventionally, brass alloy contains a small amount of lead in order toimprove the cutting property, so as to be suitable for use as a rawmaterial for making components (such as brass pipes) of a potable ordrinking water system. The brass pipes are often used in a hightemperature environment or used for delivering water containingcorrosive materials, such as chlorine.

However, lead has a relatively low melting point, and selectivecorrosion of the brass alloy-made component, such as dezincification ofthe lead-containing brass pipe, tends to occur when the brass alloy-madecomponent is used in a chlorine-containing water environment.Dezincification may seriously damage the structure of thelead-containing brass pipe, and decrease the lifespan thereof. Moreover,lead may be released from the lead-containing brass pipe into waterdelivered by the potable water system, causing water contamination.

In order to overcome the aforementioned problems regarding leadcontamination and dezincification, it is proposed to use bismuth toreplace lead in the brass alloy so as to form a lead-free brass alloy.However, since, similar to lead, bismuth has a low meltingpoint,addition thereof in the brass alloy may render the brass alloyvulnerable to cracking under the high temperature environment.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a brassalloy with dezincification inhibition capability and good cutting andmechanical properties that can overcome at least one of the aforesaiddrawbacks associated with the prior art.

According to the present invention, there is provided a brass alloy withdezincification inhibition capability and good cutting and mechanicalproperties. The brass alloy includes niobium and brass . The niobium isin an amount ranging from 0.01 to 0.15 part by weight and the brass isin an amount ranging from 99.85 to 99.99 parts by weight based on 100parts by weight of the brass alloy.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In one embodiment of the present invention, the brass alloy withdezincification inhibition capability and good cutting and mechanicalproperties includes niobium and brass. Niobium is in an amount rangingfrom 0.01 to 0.15 part by weight and brass is in an amount ranging from99.85 to 99.99 parts by weight based on 100 parts by weight of the brassalloy. At least a portion of niobium and a portion of brass are formedinto a solid solution.

With the inclusion of niobium, the dezincification inhibition capabilityand the cutting property of the brass alloy of the present invention aresignificantly improved. The reason of the improvement may be attributedto a higher melting point of niobium than that of lead. In addition,niobium is non-toxic. Hence, the brass alloy of the present invention isdurable in a high temperature environment, and does not release toxicelements.

Preferably, niobium is in an amount ranging from 0.029 to 0.077 part byweight and brass is in an amount ranging from 99.923 to 99.971 parts byweight based on 100 parts by weight of the brass alloy. More preferably,the amount of niobium is 0.077 parts by weight and the amount of brassis 99.923 parts by weight based on 100 parts by weight of the brassalloy.

Brass has an α-phase and a β-phase. Preferably, brass includes 40 to 80wt % of copper and 20 to 60 wt % of zinc based on a total weight ofbrass. More preferably, brass includes 50 to 70 wt % of copper and 30 to50 wt % of zinc based on the total weight of brass. Most preferably,brass includes 55 to 65 wt % of copper and 35 to 45 wt % of zinc basedon the total weight of brass. Brass may further include a trace of metalother than copper and zinc, e.g., Ni, Sn or Pb.

According to the present invention, a method of forming the brass alloyis provided. The method includes preparing a brass alloy compositionthat contains niobium and brass, melting the brass alloy compositionunder a temperature ranging from 1100 to 1300° C. for 5 minutes so as toform a brass alloy melt of niobium and brass, and cooling the brassalloy melt in a casting mold to 80 to 85° C. so as to form a solidsolution of niobium and brass, followed by removing the casting mold andallowing the solid solution to cool to room temperature.

Examples

The following examples are provided to illustrate the embodiment of theinvention, and should not be construed as limiting the scope of theinvention.

Sources of Chemicals

-   1.Copper block: purchased from Shin Chung Industrial

Co., Ltd.

-   2.Zinc block: purchased from Lai-I Metal Industrial Co., Ltd.-   3.Niobium powder: purchased from Well-Being Enterprise Co., Ltd.

Comparative Example (CE) Preparation of a Niobium-Free Brass Alloy

171 g copper block and 114.6 g zinc block were placed in ahigh-frequency induction furnace, followed by melting the copper blockand the zinc block under a temperature of from 1100 to 1300° C. for 5minutes to form a brass alloy melt.

The brass alloy melt was cooled in a casting mold to 80 to 85° C. so asto form a solid solution, followed by removing the casting mold andallowing the solid solution to cool to room temperature, to form theniobium-free brass alloy.

Examples 1 to 4 (EX1 to EX4) Preparation of Brass Alloy Including Brassand Niobium

The brass alloys of Examples 1 to 4 were prepared under conditionssimilar to those of Comparative Example except that each of the brassalloy compositions of Examples 1 to 4 further includes a niobium powder.

The brass alloy compositions of Examples 1 to 4 are shown in Table 1.

TABLE 1 Cu Zn Nb (g) (g) (g) EX1 186 124 0.062 EX2 173.4 115.6 0.116 EX3154.2 102.8 0.28 EX4 180.56 124.44 0.63

Evaluation Items 1. Component Analysis

Each brass alloy of Examples 1 to 4 and Comparative Example was cut intoa test piece. Each test piece was subjected to component analysis by aninductively coupled plasma mass spectrometer (ICP-MS).

The results are shown in Table 2.

TABLE 2 Element Concentration or Amount Ni Cu Zn Nb Sn Pb Test Piece ppmwt % wt % wt % ppm ppm CE 48.54 60.17 39.72 — 14.28 97.96 EX1 47.2259.22 39.58 0.029 32.22 82.12 EX2 38.55 59.88 39.12 0.051 34.11 77.53EX3 51.34 59.53 39.66 0.062 43.28 73.87 EX4 49.19 59.32 39.73 0.07735.46 80.86 Detection Limit 0.090 0.083 0.562 0.003 0.047 0.047 (ppm)Note: “—” means not added or does not exist

As shown in Table 2, the amounts of niobium in EX1 to EX4 arerespectively 0.029, 0.051, 0.062 and 0.077 part by weight based on 100parts by weight of the brass alloy. The composition of ComparativeExample is free of the niobium powder.

2. Amount of Dezincification

Each brass alloy of Examples 1to4and Comparative Example was cut into atest piece. The test pieces of Examples 1 to 4 and Comparative Examplewere subjected to dezincification test according to AS2345 Australiastandard method.

The results are shown in Table 3.

3. Cutting Property Test

Each brass alloy of Examples 1 to 4 and Comparative Example was cut intoa test piece for the cutting property test. Each test piece was placedon a drilling machine for drilling. The drilling was conducted using atitanium-plated high speed steel drill bit (size: ⅛ inch) at a drillingspeed of 1450 rpm and a drill feeding speed of 0.2 mm/sec.

The results are shown in Table 3.

TABLE 3 Amount of depth of length of Nb dezincification cutting (%) (μm)(cm) CE 0 839 6.875 EX1 0.029 121.4 5.712 EX2 0.051 113.2 4.192 EX30.062 110.9 2.875 EX4 0.077 43.6 1.007

The larger the depth of dezincification, the less the ability of thebrass alloy to prevent dezincification. As shown in Table 3, Examples 1to exhibit smaller depths of dezincification as compared to that ofComparative Example. The result indicates that the brass alloys whichinclude niobium have better dezincification inhibition capability.

In particular, the comparison shows that the depth of dezincificationdecreases from 839 μm (CE) to 43.6 μm (EX3), i.e., an increase of 95% inthe dezincification inhibition capability.

The shorter the length of the cutting, the better the cutting propertyof the brass alloy. As shown in Table 3, each of the brass alloy ofExample 1 to 4 exhibits a shorter length of cutting as compared to thatof Comparative Example. The comparison result indicates that the brassalloys which include niobium have a better cutting property.

In summary, with the inclusion of niobium in the brass alloy of thepresent invention, the dezincification inhibition capability and thecutting and mechanical properties can be improved.

While the present invention has been described in connection with whatis considered the most practical embodiment, it is understood that thisinvention is not limited to the disclosed embodiment but is intended tocover various arrangements included within the spirit and scope of thebroadest interpretation and equivalent arrangements.

What is claimed is:
 1. A method for inhibiting dezincification of brass, comprising adding niobium into brass to form a brass alloy composition, melting the brass alloy composition to form a brass alloy melt, and cooling the brass alloy melt to room temperature so as to form a brass alloy with dezincification inhibition capability, wherein, based on 100 parts by weight of said brass alloy, said niobium is in an amount ranging from 0.01 to 0.15 parts by weight, and said brass is in an amount ranging from 99.85 to 99.99 parts by weight.
 2. The method according to claim 1, wherein before cooling to room temperature, the brass alloy melt is cooled to 80 to 85° C.
 3. The method according to claim 1, wherein the step of melting the brass alloy composition is conducted under a temperature ranging from 1100 to 1300° C.
 4. The method according to claim 1, wherein, based on 100 parts by weight of said brass alloy, said niobium is in an amount ranging from 0.029 to 0.077 parts by weight and said brass is in an amount ranging from 99.923 to 99.971 parts by weight.
 5. The method according to claim 1, wherein, based on 100 parts by weight of said brass alloy, said niobium is 0.077 parts by weight and said brass is 99.923 parts by weight.
 6. The method according to claim 1, wherein said brass includes 40 to 80 wt % of copper and 20 to 60 wt % of zinc.
 7. The method according to claim 6, wherein said brass includes 50 to 70 wt % of copper and 30 to 50 wt % of zinc.
 8. The method according to claim 7, wherein said brass includes 55 to 65 wt % of copper and 35 to 45 wt % of zinc. 